The impasse between warring Republicans and Democrats on efforts to find $1.2 trillion (£767bn) in savings came as the US national debt rose above $15 trillion.

According to reports, the rival parties were preparing to announce today that they could not agree on a package of tax increases or spending cuts.

The deadline for an agreement in the so-called supercommittee was Wednesday, but the panel was charged with putting forward a plan by the end of today to give the Congressional Budget Office time to assess the true effects on the deficit.

Failure to strike a deal would trigger automatic cuts of an equivalent amount in 2013 from spending on defence and other government agencies.

The deadlock is reminiscent of the delays and arguments in July about raising the US debt ceiling. Had a last-minute deal not been struck, the US would have technically defaulted.

The wrangling was the first evidence of the leadership vacuum that has since spooked markets across the US and Europe.

Yusuf Heusen, a sales trader at IG Index, said: “News that the US has hit a stalemate on agreeing budget cuts is reminding traders of the last time lawmakers reached an impasse in the summer, and the subsequent market fallout that ensued.”